Signal.



R. M. GILSON.

SIGNAL.

APPLICATION FILED JAN.20. 1914.,

Patented May 29, 1917.

m wum INVENTOR WITNESSES UNKTED TATES PATENT ROBERT M. GILSON, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

SIGNAL.

Specification of Letters Patent.

Patented May 29, 11917.

cations both at night and in daylight. Signals embodying my invention are particularly adapted for use in railway signaling,

although they are not limited to this particular adaptatiom When a signal of the type mentioned is used on a railway curve, the beam of light projected by the signal should be visible over all points on the curve in the rear of the signal. Hence, this beam is preferably elongated in a horizontal direction, but not in a vertical direction. Furthermore, it is desirable that the beam should appearv to be about of the same intensity from all points on the curve, hence the beam preferably'varies progressively in intensity from a maximum value adjacent one end to a minimum value adjacent the other, the more intense portion of the light being directed toward the end of the curve farthest from the signal and the less intense portions being directed toward the sections of the curve nearer to the signal. Une feature of my invention is the provision of a signal which will project an elongated beam of light which variesprogressively in intensity from the maximum value adjacent one end to a minimum value adjacent the other.

I will describe several forms of signals embodying my invention, and will then point out the novel features thereof in claims.

In the acompanying drawings. Figure 1 is a top view showing one form of signal embodying my invention. Fig. 2 is a view showing in front elevation the screen 12 shown in Fig. 1. Fig. 3 is a view showing on an enlarged scale a portion of the screen 12 shown in Fig. 1, and illustrating the manner in which light rays are reflected thereby. Fig. 4 is a curve showing the-intensity of light at the various points along the line 1VW of Fig. 1. Fig. 5 is a view showing a railway curve provided with a signal er bodying my invention, and indicating portions of the curve toward which are directed the several parts of the beam indicated by the zones in Fig. 3.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1, 2 and 3, the signal here shown comprises an incandescent lamp 10 from which a beam of light comprising substantially parallel rays 13 is ,projected by a lens 11. Although I have shown an incandescent lamp as the seurce of light, it is understood that any other suitable source may be employed; and although I have shown a lens, it is understood that any other suiablo means may be employed for projecting a beam of substantially parallel value adjacent one end to a comparatively low value adjacent the other. As here shown, this screen comprises a plurality of parallel prismatic corrugations 14, 14 14t 14, 14 14, 14, 144 which corrugations I will hereinafter refer to as prisms. The rays 13 which reach each prism are, of course, refracted thereby so that on emerging from the prism they form a certain angle with the rays 13. The several prisms are so formed that the angleof refraction of each prism is different from that of any other prism, and that this angle progressively increases from prism 14:, which causes the least refraction, to prism 1%, which causes the greatest refraction. These angles of'refraction are indicated by the lines 15, 15 15*, 15, 15 15, 15, 15 which represent the direction of the rays emerging from the several prisms and from which it will be seen the angle increases progressively. Hence, the beam of light projected by the screen is elongated in the direction of line lV-QEV. thermore, these prisms vary progress area from prism 14 the area of W maximum to prismill the area of .ic minimum, hence it will be seen that the tensity of the beam varies progressive from a maximum value adjacent the responding to prism 14 to a minim adjacent the other end. This var intensity is indicated roughly by the in Fig. 4-.

The 12 in Fig.

jacent prisms in Fig. 1.

prisms 1 L whose inclined surfaces are flat, so that all the rays emerging from each prism are parallel. seen, that with this construction the rays emerging from one prism, prism 14 of Fig. 1, for example, are at an angle to all of the rays emerging from the adjacent prism 1e, hence in the beam projected from the signal there will be, theoretically at least, a dark strip 16 between the two adjacent strips of light 15 and 15 Similarly, tliare will be, theoretically at least, a dark strip between the strips of light projected by each two ad- I-Ience, theoretically, the curve shown in Fig. 4 would be broken at intervals by parts which would drop abruptly to the base line. In practice, however, owing to inaccuracies in the surfaces of the lens 11 and screen 12, and owing also to the fact that the filament of lamp 10 cannot be concentrated at the focus of the lens, the rays from adjacent prisms will actually blend together so that there will be no dark strips which can readily be detected by the eye; that is, the intensity of the light will appear to vary smoothly as indicated in Fig. 4. I

In Fig. 5 I have shown a railway curve F, at one end of which is a signal S of the type shown in Fig. 1, and which projects a beam varying in intensity substantially as indicated by Fig. 4. Signal S is so located that the portion A of the beam projected by the signal is directed toward section A of the curve, portion B toward B, etc. That is, the most intense portion of the beam is directed toward the section of the curve farthest from the signal, and the portions of the beam of progressively decreasing intensity are directed toward the sections of the curve progressively approaching the signal. Hence, as an observer passes along the curve F toward the signal, the beam. of light is constantly visible, and constantly appears of substantially the same intensity. There is, therefore. no light wasted in unnecessarily intense illumination at any one part of the curve.

Although I have herein shown only one form of signal embodying my invention, it

is understood that various changes and modifications may be made therein Within I the scope of the appended claims without departing from the spirit and scope of my invention.

From Fig. 3 it will be Having thus described my invention, what I claim is:

1. A signal adapted for use on a railway curve and comprising a source of light, means for projecting from said source a beam of substantially parallel rays, and a glass screen locatedin said beam and comprising a series of vertically disposed prisms increasing inangle and decreasing in area from one side of the beam toward the other, said beam-projecting means and said screen being so placed that the portion of the beam which is deflected through the greatest angle is directed toward one end of the curve and the portion of the beam which is deflected throughthe least angle is directed toward the other end of the curve.

2. A signal adapted for use on a railway curve and comprising a source of light, means for projecting from said source a beam of substantially parallel rays, and a glass screen located in said beam and comprising a series of vertically disposed prisms increasing progressively in angle from one side of the beam toward the other, said beam-projecting means and said screen being so placed that the portion of the beam which is deflected through the greatest angle is directed toward one end of the curve and the portion of the beam which is deflected through the least angle is directed toward the other end of the curve.

3. A signal adapted for use on a railway curve and comprising a source of light,

- means for projecting from said source a 'beam of substantially parallel rays, and a glass screen located in said beam and comprising a series of vertically disposed prisms increasing progressively in angle from one side of the beam toward the other, said prisms also decreasing progressively in area from one side of the beam toward the other,

I said beam projecting means and said screen being so placed that the portion of the beam having the greatest intensity is directed toward the far end of the curve and the portion of the beam having the lowest intensity is directed toward the part of the curve nearest the signal.

In testimony whereof Iafix my signature in presence of two witnesses.

ROBERT M. GILSON. Witnesses:

A. HmMAN Banana, It. I1. Krs'rnnn. 

